/**
 * Copyright (c) 2005-2010 springside.org.cn
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * 
 * $Id: ServletUtils.java 1211 2010-09-10 16:20:45Z calvinxiu $
 */
package cn.newtouch.util;

import java.io.UnsupportedEncodingException;
import java.util.Enumeration;
import java.util.Map;
import java.util.StringTokenizer;
import java.util.TreeMap;

import javax.servlet.ServletRequest;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.springframework.util.Assert;

/**
 * Http与Servlet工具类.
 * 
 * @author calvin
 */
public class ServletUtils
{

    // -- Content Type 定义 --//
    public static final String TEXT_TYPE             = "text/plain";

    public static final String JSON_TYPE             = "application/json";

    public static final String XML_TYPE              = "text/xml";

    public static final String HTML_TYPE             = "text/html";

    public static final String JS_TYPE               = "text/javascript";

    public static final String EXCEL_TYPE            = "application/vnd.ms-excel";

    // -- Header 定义 --//
    public static final String AUTHENTICATION_HEADER = "Authorization";

    // -- 常用数值定义 --//
    public static final long   ONE_YEAR_SECONDS      = 60 * 60 * 24 * 365;

    /**
     * 设置客户端缓存过期时间 的Header.
     */
    public static void setExpiresHeader(HttpServletResponse response,
            long expiresSeconds)
    {
        // Http 1.0 header
        response.setDateHeader("Expires", System.currentTimeMillis()
                + expiresSeconds * 1000);
        // Http 1.1 header
        response.setHeader("Cache-Control", "private, max-age="
                + expiresSeconds);
    }

    /**
     * 设置禁止客户端缓存的Header.
     */
    public static void setDisableCacheHeader(HttpServletResponse response)
    {
        // Http 1.0 header
        response.setDateHeader("Expires", 1L);
        response.addHeader("Pragma", "no-cache");
        // Http 1.1 header
        response.setHeader("Cache-Control", "no-cache, no-store, max-age=0");
    }

    /**
     * 设置LastModified Header.
     */
    public static void setLastModifiedHeader(HttpServletResponse response,
            long lastModifiedDate)
    {
        response.setDateHeader("Last-Modified", lastModifiedDate);
    }

    /**
     * 设置Etag Header.
     */
    public static void setEtag(HttpServletResponse response, String etag)
    {
        response.setHeader("ETag", etag);
    }

    /**
     * 根据浏览器If-Modified-Since Header, 计算文件是否已被修改.
     * 
     * 如果无修改, checkIfModify返回false ,设置304 not modify status.
     * 
     * @param lastModified
     *            内容的最后修改时间.
     */
    public static boolean checkIfModifiedSince(HttpServletRequest request,
            HttpServletResponse response, long lastModified)
    {
        long ifModifiedSince = request.getDateHeader("If-Modified-Since");
        if ((ifModifiedSince != -1) && (lastModified < ifModifiedSince + 1000))
        {
            response.setStatus(HttpServletResponse.SC_NOT_MODIFIED);
            return false;
        }
        return true;
    }

    /**
     * 根据浏览器 If-None-Match Header, 计算Etag是否已无效.
     * 
     * 如果Etag有效, checkIfNoneMatch返回false, 设置304 not modify status.
     * 
     * @param etag
     *            内容的ETag.
     */
    public static boolean checkIfNoneMatchEtag(HttpServletRequest request,
            HttpServletResponse response, String etag)
    {
        String headerValue = request.getHeader("If-None-Match");
        if (headerValue != null)
        {
            boolean conditionSatisfied = false;
            if (!"*".equals(headerValue))
            {
                StringTokenizer commaTokenizer = new StringTokenizer(
                        headerValue, ",");

                while (!conditionSatisfied && commaTokenizer.hasMoreTokens())
                {
                    String currentToken = commaTokenizer.nextToken();
                    if (currentToken.trim().equals(etag))
                    {
                        conditionSatisfied = true;
                    }
                }
            }
            else
            {
                conditionSatisfied = true;
            }

            if (conditionSatisfied)
            {
                response.setStatus(HttpServletResponse.SC_NOT_MODIFIED);
                response.setHeader("ETag", etag);
                return false;
            }
        }
        return true;
    }

    /**
     * 设置让浏览器弹出下载对话框的Header.
     * 
     * @param fileName
     *            下载后的文件名.
     */
    public static void setFileDownloadHeader(HttpServletResponse response,
            String fileName)
    {
        try
        {
            // 中文文件名支持
            String encodedfileName = new String(fileName.getBytes(),
                    "ISO8859-1");
            response.setHeader("Content-Disposition", "attachment; filename=\""
                    + encodedfileName + "\"");
        }
        catch (UnsupportedEncodingException e)
        {
        }
    }

    /**
     * 取得带相同前缀的Request Parameters.
     * 
     * 返回的结果的Parameter名已去除前缀.
     */
    @SuppressWarnings("unchecked")
    public static Map<String, Object> getParametersStartingWith(
            ServletRequest request, String prefix)
    {
        Assert.notNull(request, "Request must not be null");
        Enumeration paramNames = request.getParameterNames();
        Map<String, Object> params = new TreeMap<String, Object>();
        if (prefix == null)
        {
            prefix = "";
        }
        while (paramNames != null && paramNames.hasMoreElements())
        {
            String paramName = (String) paramNames.nextElement();
            if ("".equals(prefix) || paramName.startsWith(prefix))
            {
                String unprefixed = paramName.substring(prefix.length());
                String[] values = request.getParameterValues(paramName);
                if (values == null || values.length == 0)
                {
                    // Do nothing, no values found at all.
                }
                else
                    if (values.length > 1)
                    {
                        params.put(unprefixed, values);
                    }
                    else
                    {
                        params.put(unprefixed, values[0]);
                    }
            }
        }
        return params;
    }
}